A Series of Room-Temperature Thermally Stable Bromostannylenes Bearing the Bulky Rind Group: Synthesis, Characterization, and Crystal Structures

A series of bromostannylenes, (Rind)BrSn: (1; Rind = EMind (a, R-1 = Et, R-2 = Me), Eind (b, R-1 = R-2 = Et), MPind (c, R-1= Me, R-2 = Pr-n)), have been obtained as roomtemperature thermally stable crystalline materials incorporating the fused-ring bulky Rind groups (Rind = 1,1,7,7-tetra-R-1-3,3,5,5-tetra-R-2-s-hydrindacen-4-yl). The bulky Eind- and the bulkier MPind-based bromostannylenes (1b,c) have been synthesized by the reaction of SnBr2.(dioxane) with 1 equiv of (Rind)Li in THF. In contrast, the less bulky EMind-based halostannylenes (EMind)- XSn: (X = Br (1a), Cl (2a)) have been prepared by a ligand redistribution reaction between the diarylstannylene (EMind)(2)Sn: (3a) and SnX2.(dioxane) (X = Br, Cl), in toluene. The crystal structures of (EMind)BrSn: (1a), (Eind)BrSn: (1b), and (MPind)BrSn: (1c) have been determined by X-ray diffraction methods along with that of (EMind)C1Sn: (2a). While the bulkier MPind-based 1c has a monomeric structure with a bent two-coordinate Sn(II) center, a coordination dimer was found for the Eind-based 1b in which two Sn atoms are asymmetrically bridged by two Br atoms. The less bulky EMind-based 1a and 2a show a unique one-dimensional (1-D) polymeric structure in their crystals with alternating Sn and Br or Cl atoms supported by the perpendicularly oriented EMind groups. The halostannylenes 1a-c and 2a all exist as monomers in solution on the basis of their spectroscopic data, and their electronic properties have been experimentally and theoretically characterized.

Automated summary

A series of bromostannylenes with different substituents have been obtained and their crystal structures have been determined by X-ray diffraction methods. The bulkier species exhibit monomeric structures, while the less bulky ones show polymeric structures in crystals. These compounds exist as monomers in solution.